The continue keyword has two meanings.
It can introduce a continue block after a loop,
or it can exit the current when block.
Up till now,
the latter meaning was only valid with the "switch" feature enabled,
and was a syntax error otherwise.
Since the main purpose of feature.pm is to avoid conflicts with user-defined subroutines,
there is no reason for continue to depend on it.

$$ was made read-only in Perl 5.8.0.
But only sometimes: local $$ would make it writable again.
Some CPAN modules were using local $$ or XS code to bypass the read-only check,
so there is no reason to keep $$ read-only.
(This change also allowed a bug to be fixed while maintaining backward compatibility.)

Attempting to tie a scalar after a typeglob was assigned to it would instead tie the handle in the typeglob's IO slot.
This meant that it was impossible to tie the scalar itself.
Similar problems affected tied and untie: tied $scalar would return false on a tied scalar if the last thing returned was a typeglob,
and untie $scalar on such a tied scalar would do nothing.

We fixed this problem before Perl 5.14.0,
but it caused problems with some CPAN modules,
so we put in a deprecation cycle instead.

Now the deprecation has been removed and this bug has been fixed.
So tie $scalar will always tie the scalar,
not the handle it holds.
To tie the handle,
use tie *$scalar (with an explicit asterisk).
The same applies to tied *$scalar and untie *$scalar.

Previously,
if one embeds Perl or uses XS and calls fork(3) from C,
Perls notion of $$ could go out of sync with what getpid() returns.
By always fetching the value of $$ via getpid(),
this potential bug is eliminated.
Code that depends on the caching behavior will break.
As described in "Core Enhancements",
$$ is now writable,
but it will be reset during a fork.

The documentation for $! has been corrected and clarified.
It used to state that $!
could be undef,
which is not the case.
It was also unclear as to whether system calls set C's errno or Perl's $! [perl #91614].

Documentation for $$ has been amended with additional cautions regarding changing the process ID.

regexp.h has been modified for compatibility with GCC's -Werror option,
as used by some projects that include perl's header files (5.14.1).

USE_LOCALE{,_COLLATE,_CTYPE,_NUMERIC} have been added the output of perl -V as they have affect the behaviour of the interpreter binary (albeit only in a small area).

The code and tests for IPC::Open2 have been moved from ext/IPC-Open2 into ext/IPC-Open3,
as IPC::Open2::open2() is implemented as a thin wrapper around IPC::Open3::_open3(),
and hence is very tightly coupled to it.

The magic types and magic vtables are now generated from data in a new script regen/mg_vtable.pl,
instead of being maintained by hand.
As different EBCDIC variants can't agree on the code point for '~',
the character to code point conversion is done at build time by generate_uudmap to a new generated header mg_data.h.
PL_vtbl_bm and PL_vtbl_fm are now defined by the pre-processor as PL_vtbl_regexp,
instead of being distinct C variables.
PL_vtbl_sig has been removed.

Building with -DPERL_GLOBAL_STRUCT works again.
This configuration is not generally used.

Perl configured with MAD now correctly frees MADPROP structures when OPs are freed.
MADPROPs are now allocated with PerlMemShared_malloc()

The compiled representation of formats is now stored via the mg_ptr of their PERL_MAGIC_fm.
Previously it was stored in the string buffer,
beyond SvLEN(),
the regular end of the string.
SvCOMPILED() and SvCOMPILED_{on,off}() now exist solely for compatibility for XS code.
The first is always 0,
the other two now no-ops.
(5.14.1)

Some global variables have been marked const,
members in the interpreter structure have been re-ordered,
and the opcodes have been re-ordered.
The op OP_AELEMFAST has been split into OP_AELEMFAST and OP_AELEMFAST_LEX.

When empting a hash of its elements (e.g.
via undef(%h),
or %h=()),
HvARRAY field is no longer temporarily zeroed.
Any destructors called on the freed elements see the remaining elements.
Thus,
%h=() becomes more like delete $h{$_} for keys %h.

Boyer-Moore compiled scalars are now PVMGs,
and the Boyer-Moore tables are now stored via the mg_ptr of their PERL_MAGIC_bm.
Previously they were PVGVs,
with the tables stored in the string buffer,
beyond SvLEN().
This eliminates the last place where the core stores data beyond SvLEN().

Simplified logic in Perl_sv_magic() introduces a small change of behaviour for error cases involving unknown magic types.
Previously,
if Perl_sv_magic() was passed a magic type unknown to it,
it would

Croak "Modification of a read-only value attempted" if read only

Return without error if the SV happened to already have this magic

otherwise croak "Don't know how to handle magic of type \\%o"

Now it will always croak "Don't know how to handle magic of type \\%o",
even on read only values,
or SVs which already have the unknown magic type.

The new (in 5.14.0) regular expression modifier /a when repeated like /aa forbids the characters outside the ASCII range that match characters inside that range from matching under /i.
This did not work under some circumstances,
all involving alternation,
such as:

"\N{KELVIN SIGN}" =~ /k|foo/iaa;

succeeded inappropriately. This is now fixed.

5.14.0 introduced some memory leaks in regular expression character classes such as [\w\s], which have now been fixed (5.14.1)

An edge case in regular expression matching could potentially loop. This happened only under /i in bracketed character classes that have characters with multi-character folds, and the target string to match against includes the first portion of the fold, followed by another character that has a multi-character fold that begins with the remaining portion of the fold, plus some more.

"s\N{U+DF}" =~ /[\x{DF}foo]/i

is one such case. \xDF folds to "ss". (5.14.1)

A few characters in regular expression pattern matches did not match correctly in some circumstances, all involving /i. The affected characters are: COMBINING GREEK YPOGEGRAMMENI, GREEK CAPITAL LETTER IOTA, GREEK CAPITAL LETTER UPSILON, GREEK PROSGEGRAMMENI, GREEK SMALL LETTER IOTA WITH DIALYTIKA AND OXIA, GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS, GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND OXIA, GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS, LATIN SMALL LETTER LONG S, LATIN SMALL LIGATURE LONG S T, and LATIN SMALL LIGATURE ST.

A number of edge cases have been fixed with formats and formline; in particular, where the format itself is potentially variable (such as with ties and overloading), and where the format and data differ in their encoding. In both these cases, it used to possible for the output to be corrupted [perl #91032].

formline no longer converts its argument into a string in-place. So passing a reference to formline no longer destroys the reference [perl #79532].

Copy-on-write scalars were introduced in 5.8.0, but most Perl code did not encounter them (they were used mostly internally). Perl 5.10.0 extended them, such that assigning __PACKAGE__ or a hash key to a scalar would make it copy-on-write. Several parts of Perl were not updated to account for them, but have now been fixed.

utf8::decode had a nasty bug that would modify copy-on-write scalars' string buffers in place (i.e., skipping the copy). This could result in hashes having two elements with the same key [perl #91834].

Lvalue subroutines were not allowing COW scalars to be returned. This was fixed for lvalue scalar context in Perl 5.12.3 and 5.14.0, but list context was not fixed until this release.

Note: There are still some discrepancies between explicit and implicit return, which will hopefully be resolved soon. So the exact behaviour is not set in stone yet.

Lvalue subroutines used to enforce lvalue syntax (i.e., whatever can go on the left-hand side of =) for the last statement and the arguments to return. Since lvalue subroutines are not always called in lvalue context, this restriction has been lifted.

Lvalue subroutines are less restrictive as to what values can be returned. It used to croak on values returned by shift and delete and from other subroutines, but no longer does so [perl #71172].

Empty lvalue subroutines (sub :lvalue {}) used to return @_ in list context. In fact, all subroutines used to, but regular subs were fixed in Perl 5.8.2. Now lvalue subroutines have been likewise fixed.

Lvalue subroutines used to copy their return values in rvalue context. Not only was this a waste of CPU cycles, but it also caused bugs. A ($) prototype would cause an lvalue sub to copy its return value [perl #51408], and while(lvalue_sub() =~ m/.../g) { ... } would loop endlessly [perl #78680].

Autovivification now works on values returned from lvalue subroutines [perl #7946].

When called in pass-by-reference context (e.g., subroutine arguments or a list passed to for), an lvalue subroutine returning arrays or hashes used to bind the arrays (or hashes) to scalar variables--something that is not supposed to happen. This could result in "Bizarre copy of ARRAY" errors or print ignoring its arguments. It also made nonsensical code like @{\$_} "work". This was fixed in 5.14.0 if an array were the first thing returned from the subroutine (but not for $scalar, @array or hashes being returned). Now a more general fix has been applied [perl #23790].

When called in pass-by-reference context, lvalue subroutines used to copy any read-only value that was returned. E.g., sub :lvalue { $] } would not return $], but a copy of it.

Assignment to keys returned from an lvalue sub used not to work, but now it does.

Applying the :lvalue attribute to an XSUB or to an aliased subroutine stub with sub foo :lvalue; syntax stopped working in Perl 5.12. This has been fixed.

A bug has been fixed that would cause a "Use of freed value in iteration" error if the next two hash elements that would be iterated over are deleted [perl #85026]. (5.14.1)

Freeing deeply nested hashes no longer crashes [perl #44225].

Deleting the current hash iterator (the hash element that would be returend by the next call to each) in void context used not to free it. The hash would continue to reference it until the next iteration. This has been fixed [perl #85026].

Passing the same constant subroutine to both index and formline no longer causes one or the other to fail [perl #89218]. (5.14.1)

List assignment to lexical variables declared with attributes in the same statement (my ($x,@y) : blimp = (72,94)) stopped working in Perl 5.8.0. It has now been fixed.

Perl 5.10.0 introduced some faulty logic that made "U*" in the middle of a pack template equivalent to "U0" if the input string was empty. This has been fixed [perl #90160].

Destructors on objects were not called during global destruction on objects that were not referenced by any scalars. This could happen if an array element were blessed (e.g., bless \$a[0]) or if a closure referenced a blessed variable (bless \my @a; sub foo { @a }).

Now there is an extra pass during global destruction to fire destructors on any objects that might be left after the usual passes that check for objects referenced by scalars [perl #36347].

This bug fix was added in Perl 5.13.9, but caused problems with some CPAN modules that were relying on the bug. Since it was so close to Perl 5.14.0, the fix was reverted in 5.13.10, to allow more time for the modules to adapt. Hopefully they will be fixed soon (see "Known Problems", below).

given was not calling set-magic on the implicit lexical $_ that it uses. This meant, for example, that pos would be remembered from one execution of the same given block to the next, even if the input were a different variable [perl #84526].

The "R" command for restarting a debugger session has been fixed to work on Windows, or any other system lacking a POSIX::_SC_OPEN_MAX constant [perl #87740].

Fixed a case where it was possible that a freed buffer may have been read from when parsing a here document [perl #90128]. (5.14.1)

The study function could become confused if fed a string longer than 2**31 characters. Now it simply skips such strings.

each(ARRAY) is now wrapped in defined(...), like each(HASH), inside a while condition [perl #90888].

In @INC filters (subroutines returned by subroutines in @INC), $_ used to misbehave: If returned from a subroutine, it would not be copied, but the variable itself would be returned; and freeing $_ (e.g., with undef *_) would cause perl to crash. This has been fixed [perl #91880].

An ASCII single quote (') in a symbol name is meant to be equivalent to a double colon (::) except at the end of the name. It was not equivalent if followed by a null character, but now it is [perl #88138].

The abbreviations for four C1 control characters MWPM, RI, and ST were previously unrecognized by \N{}, vianame(), and string_vianame().

Some cases of threads crashing due to memory allocation during cloning have been fixed [perl #90006].

Attempting to goto out of a tied handle method used to cause memory corruption or crashes. Now it produces an error message instead [perl #8611].

Perl skips copying values returned from a subroutine if it thinks the value is not in use elsewhere. Due to faulty logic, this would happen with the result of delete, shift or splice, even if the result was referenced elsewhere. So \sub { delete $_[0] }->($x) would return a reference to $x. This has been fixed [perl #91844].

The list above is almost certainly incomplete as it is automatically generated from version control history. In particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the perlbug program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of perl -V, will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.